is.js
A collection of user-defined type guards to handle some of Javascript's less-than-ideal behavior.
Installing
$ npm install is-js
$ yarn add is-jsUsage
array
▸ array(arg): arg is any[]
Determines if the argument is an array.
remarks
Defaults to the native Array.isArray method, if present.
Parameters
| Name | Type |
|---|---|
arg |
any |
Returns
arg is any[]
true if the given argument is an array
bigint
▸ bigint(value): boolean
Determines if the argument is a BigInt
remarks
This method does not support polyfilled BigInt implementations; please defer
to the library in use to determine the type of an unknown argument.
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
boolean
true if the given argument is a native BigInt
bool
▸ bool(value): value is boolean
Determines if the argument is a boolean
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is boolean
true if the given argument is a boolean
date
▸ date(value): value is Date
Determines if the argument is a date.
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is Date
true if the given argument is a date
error
▸ error(value): value is Error
Determines if the argument is an error.
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is Error
true if the given argument is an error
func
▸ func(value): value is Function
Determines if the argument is a function.
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is Function
true if the given argument is a function
nil
▸ nil(value): value is null
Determines if the argument is null
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is null
true if the given argument is null
number
▸ number(value): value is number
Determines if the argument is a number
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is number
true if the given argument is a number
object
▸ object(value): value is Object
Determines if the argument is an object.
remarks
Nearly everything in Javascript is an object; this method discerns between
native primitives (e.g. true, 3, some text) and their object-wrapped
variants (Boolean, Number, String)
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is Object
true if the given argument is an object
promise
▸ promise(value): value is Promise<unknown>
Determines if the argument is a native promise.
remarks
Some libraries and frameworks still include their own polyfilled Promises,
in which case this method is unreliable. If you are using such a library,
please defer to the provided Promise implementation or use promiseLike
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is Promise<unknown>
true if the given argument is a string
promiseLike
▸ promiseLike(value): value is Object
Determines if the argument conforms to the minimal interface of a Promise;
that is, it has a method named then.
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is Object
true if the given argument conforms to the Promise interface
regex
▸ regex(value): value is RegExp
Determines if the argument is a regular expression.
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is RegExp
true if the given argument is a regular expression
string
▸ string(value): value is string
Determines if the argument is a string.
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is string
true if the given argument is a string
symbol
▸ symbol(value): value is Symbol
Determines if the argument is a symbol
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is Symbol
true if the given argument is a symbol
undef
▸ undef(value): value is undefined
Determines if the argument is undefined
Parameters
| Name | Type | Description |
|---|---|---|
value |
unknown |
Value in question |
Returns
value is undefined
true if the given argument is undefined